### Introduction

1 This publication contains projections of the population of Australia, each state and territory and each capital city and rest of state region, by age and sex for the period 2018 to 2066. Capital city/rest of state projections were not generated for the Australian Capital Territory because under the Australian Statistical Geography Standard, the Australian Capital Territory is not broken down into capital city and rest of state regions.

2 Three series of projections (high, medium and low series) feature in this publication. These series have been selected to provide a range, although not the full range, of projections for analysis and discussion. All 72 series are available via ABS.Stat datasets.

3 For some states and territories, high and low series do not depict the highest or lowest population outcomes. Where applicable, other series have been included in commentary.

4 These projections supersede the 2012-based series published in Population Projections, Australia, 2012 (base) to 2101 (cat. no. 3222.0) in November 2013.

5 The projections for Australia include Other Territories, comprising of Christmas Island, Cocos (Keeling) Islands, Jervis Bay Territory and Norfolk Island.

### Background

6 The ABS publishes population projections following each five-yearly Census.

7 The projections are not intended as predictions or forecasts, but are illustrations of growth and change in the population that would occur if assumptions made about future demographic trends were to prevail over the projection period.

8 While the assumptions for the projections are formulated on the basis of an assessment of past demographic trends, both in Australia and overseas, there is no certainty that any of the assumptions will or will not be realised. In addition, no assessment has been made of changes in non-demographic conditions.

9 Accordingly, alternative combinations of assumptions have been provided in recognition of this uncertainty and to provide users with a range of options.

### Development

10 The process of developing population projections involves research, analysis, consultation and computation. Analysis of demographic trends, research into the determinants of population growth and distribution, and consultation with various experts at the national and state levels are necessary to formulate the various assumptions and to ensure their general relevance for the projection period.

11 A consultation process, involving expert academic and government demographers, occurred from May to July 2018, following which assumptions for the population projections were finalised by the Australian Bureau of Statistics (ABS). Three assumptions were used for fertility, two for mortality, three for net overseas migration and three for net interstate migration. In addition, a zero net overseas migration assumption has been included to illustrate the contribution of overseas migration to Australia.

### Projection techniques

12 There are many techniques which may be used for population projections, such as simple extrapolations, probabilistic methods, broad economic, social and time-series analysis, and detailed component methods.

13 The ABS uses the cohort-component method, which begins with a base population for each sex by single year of age and advances it year by year by applying assumptions regarding future fertility, mortality and migration. This procedure is repeated for each year in the projection period for Australia and each state and territory, as well as each capital city and rest of state region in each state and territory. The resulting population projections for each year for the states and territories, by sex and single year of age, are adjusted to sum to the Australian results. Likewise, capital city and rest of state projections are adjusted to sum to their respective state and territory projections. The projection method is detailed in Demographic Estimates and Projections: Concepts, Sources and Methods (cat. no. 3228.0).

### Assumptions

14 Assumptions regarding future levels of fertility, mortality and migration used to produce the population projections, and how they were formulated, are presented in the section 'Assumptions'.

### Acknowledgement

15 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated; without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.

### Additional statistics available

16 As well as the statistics included in this and related publications, the ABS may have other relevant data available on request. Inquiries should be made to the National Information and Referral Service on 1300 135 070.